Various image fusion techniques have been conducted to merge various sensors data. However, when the existing image fusion processes are applied to the IKONOS images, the spectral distortion is appeared. To investigate this distortion problem, this work presents a study indicating that there are two reasons where the distortion of the spectrum is caused. To solve this color distortion problem, we proposed an image fusion process using Steepest Decent method which improves the correlation coefficients between the original 4m MS image and the fused 1m MS image. To evaluate our proposed image fusion process, the correlation coefficient between original MS (R, G and B) image and fused MS image and their average value have been compared for the correctness of spectral quality. Moreover the comparison among the proposed technique and existing processes (IHS image fusion, Brovey Transform, Principal Component Analysis) has been done. Our method has reduced the spectral distortion problem.